Paper felts or mats

ABSTRACT

A paper felt or mat is made from an aqueous slurry or dispersion of kraft wood pulp, a number of compounding ingredients such as finely divided inorganic pigments and fillers, a binder, an anionic latex of a copolymer wherein the core of the copolymer comprises a copolymer of a vinyl aryl monomer and a dicarboxylic acid monomer such as fumaric acid and/or itaconic acid and wherein the shell comprises a copolymer or a vinyl aryl monomer, a conjugated diene monomer, a glycidyl monomer such as glycidyl acrylate and/or glycidyl methacrylate and optionally a monocarboxylic acid monomer such as acrylic acid and/or methacrylic acid. The mat of this invention exhibits improved properties over mats made from other latex binders.

This application is a continuation of application Ser. No. 07/637,912,filed on Jan. 7, 1991, now abandoned, which is a continuation of U.S.Ser. No. 484,601 now of U.S. Pat. No. 5,002,982 Terry C. Neubert, for"Paper Felts or Mats".

This invention relates to a polymeric binder, to a method for makingsaid binder and to felts or paper mats.

BACKGROUND

Paper felts or mats are formed from an aqueous slurry of kraft woodpulp, a predominant amount of finely divided inorganic fillers, a latexbinder and other ingredients such as antioxidants, biocides andflocculants. The slurry is cast onto a fourdrinier machine or rotarydrum machine from a head box where the water is largely removed, pressedto form a sheet which is then passed over drying cans, cooling cans,calendered and wound on a reel.

To form a flooring tile, the felt or mat is unwound from the reel,passed to a conveyor where the top layer of the mat is coated with avinyl plastisol which is fluxed and cooled to form a vinyl coating whichis then printed to form a design on the vinyl coating of the mat sheet.The design is then overcoated with a hot melt vinyl coating compositionand cooled to form an abrasion-resistant top coating.

An object of this invention is to provide a novel polymeric binder forpaper felts or mats.

Another object of this invention is to provide a method for making anovel polymeric binder.

Still another object of this invention to provide an improved paper feltor mat.

These and other objects and advantages of the present invention willbecome more apparent to those skilled in the art from the followingdescription and examples.

SUMMARY OF THE INVENTION

According to the present invention, an improved paper felt or mat isprovided wherein the latex or polymeric binder used in the paper makingprocess comprises an anionic emulsion of a polymeric binder comprising acore-shell copolymer wherein the core comprises a copolymer of a vinylaryl monomer and fumaric and/or itaconic acid and a shell of a copolymerof a vinyl aryl monomer, a conjugated diene, glycidylacrylate and/orglycidylmethacrylate and optionally acrylic acid and/or methacrylicacid.

The core-shell copolymer latex is then mixed with the kraft wood pulpand compounding ingredients for the paper felt or mat, dewatered, driedand compressed to form a paper felt or mat.

DISCUSSION OF DETAILS AND PREFERRED EMBODIMENTS

In the core the vinyl aryl monomer having from 8 to 10 carbon atoms maybe selected from the group consisting of styrene, alphamethyl styrene,paramethyl styrene, methylvinyl toluene, p-vinyl toluene and s-ethylstyrene. Styrene is preferred. The styrene is used in an amount of from6 to 8 parts by weight and the fumaric and/or itaconic acid are used inan amount of from 0.50 to 8 parts. Fumaric acid is preferred.

In the shell, the conjugated diene monomer has from 4 to 6 carbon atomsselected from the group consisting of 1,3-butadiene (preferred),isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, pentadiene andhexadiene and where the vinyl aryl monomer has from 8to 10 carbon atomsand can be selected from the group consisting of styrene (preferred),alphamethyl styrene, paramethyl styrene, methylvinyl toluene, p-vinyltoluene and 3-ethyl styrene. The vinyl aryl monomer is used in a amountof from about 40 to 60 parts by weight and the conjugated diene monomeris used in an amount of from 60 to 40 parts. The glycidyl acrylateand/or glycidyl methacrylate (preferred) is used in the amount of from1.5 to 5.0 parts. The acrylic and/or methacrylic acid (if used, it ispreferred) are employed in an amount of 0 to 2.0 parts.

The copolymer core is first formed by free radical emulsionpolymerization, followed by the addition of monomers to form the shellcopolymer.

Of the core-shell copolymer, the core comprises about 7.5 to 10.5 andthe shell comprises from 92.5 to 89.5 parts.

Polymerization of the monomers to form the core and shell is effected byfree-radical initiators (free-radical formers or free-radical formingsystems, catalysts) such as ammonium, potassium or sodium persulfate, H₂O₂ and the like in an amount sufficient for polymerization of themonomers and to obtain the desired molecular weight. Other free-radicalinitiators can be used which decompose or become active at thetemperature used during polymerization. Examples of some otherfree-radical initiators are cumene hydroperoxide, dibenzoyl peroxide,diacetyl peroxide, didecanoyl peroxide, di-t-butyl peroxide, dilauroylperoxide, bis (p-methoxy benzoyl) peroxide, t-butyl peroxy pivalate,dicumyl peroxide, isopropyl percarbonate, di-sec-butyl,peroxydicarbonate, azobis-dimethyl-valeronitrile,2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile and2,2'-azobis (methylisobutyrate) and the like and mixtures of the same.Only minor amounts of initiators are necessary to effect polymerization.

Emulsifiers such as soaps, surfactants or dispersing agents are used inan amount sufficient to obtain an aqueous emulsion of the water andmonomers and resulting polymers. Examples of some emulsifiers arepotassium laurate, potassium soap of disproportionated rosin, potassiumstearate, potassium oleate, sodium lauryl sulfate,na-dodecyldiphenyloxide disulfonate, di-iso butylsodiumsulfosuccinate,sodium dodecylsulfonate, sodiumdecylsulfate, sodium salt of condensednaphthalene sulfonic acid and sodium rosinate and the like and mixturesthereof. Other well know surfactants can be used.

Chain transfer agents or modifiers are well known in the emulsioncopolymerization of vinyl and diene monomers to make polymers. They areused generally to modify the molecular weight and to reducecross-linking. While many types have been proposed, it is preferred touse the alkyl and/or alkylaryl mercaptans having from 8 to 18 carbonatoms. Of these, the tertiary alkyl mercaptans are much preferred.Examples of some mercaptans are n-octyl mercaptan, n-dodecyl mercaptan(preferred), t-octyl mercaptan, t-dodecyl mercaptan, p-tridecylmercaptan, tetradecyl mercaptan, hexadecyl mercaptan and so forth andthe mixtures thereof.

NaOH, KOH, NH₄ OH and so forth may be added to the polymerizationreactor before, during or after polymerization to control the pH asdesired.

The water should be free of deleterious materials, and preferably shouldbe distilled or ion exchanged. Sufficient water is used to enableformation of the emulsions and to enable proper mixing or stirring ofthe ingredients during polymerization to obtain the desired rate anddegree of polymerization, heat transfer and so forth. The solids contentof the resulting aqueous alkaline latices or dispersions or copolyersmay vary from about 35 to 55% by weight, and the pH can be from about7.0 to 11.5.

Stabilizers, antioxidants and chelating agents may be used duringpolymerization. Also the use of shortstops at the end of free radicalpolymerization is well known; they are not only used to stop thepolymerization in the reactor at the desired conversion but also toprevent further polymerization, cross-linking, etc. during stripping,work-up and so forth. Examples of some shortstops are hydroquinone,sodium sulfide, hydroxyl ammonium acid sulfate, hydroxyl ammoniumsulfate, sodium diethyl dithiocarbamate, diethylhydroxylamine(preferred), sodium dimethyl dithiocarbamate, potassium dimethyldithiocarbamate, dimethylammonium dimethyldithiocarbamate, hydroxylaminesulfate plus sodium hydrosulfite and so forth.

Temperatures used during polymerization should be sufficient to effectpolymerization by activation of the initiator and double bonds of themonomers. They should not be too high to cause a run-away reaction andnot too low to retard polymerization. In general, the temperature may befrom about 125to 175° F.

Polymerization should be conducted in a pressure reactor, fitted with astirrer or other agitating means, heating and cooling means, with meansto flush with or pump in an inert gas such as nitrogen, helium, argon,neon and the like in order to polymerize preferably under inert ornon-reactive conditions, with means to charge the monomers, water,initiators and so forth, venting means, and with means to recover thepolymer and so forth. The reactor should be cleaned or flushed outbetween polymerization runs to remove traces of shortstops, initiators,modifiers, residues and so forth which might interfere with subsequentpolymerizations. There should be sufficient agitation or stirring of thepolymerization media to ensure thorough mixing, diffusion, contact andso forth. All of the polymerization ingredients except the shortstop maybe charged to the reactor at the same time, intermittently,incrementally or continuously. Also, the ingredients may be addedseparately or in a mixture.

The polymers are, thus, made in water using free radical initiators,chelating agents, modifiers, emulsifiers, surfactants, stabilizers,fungicides, short stopping agents and so forth by known techniques.Polymerization may be carried to about 100% conversion.

On a dry weight basis the aqueous slurry to form the paper felt or matcomprises from about parts by weight:

Kraft wood pulp 5.0 to 20.0

Polyethylene particles 0.5 to 3.0 to improve pulping

Finely divided clay 60.0 to 85.0 or talc (clay preferred)

Glass fibers, chopped 1.0 to 2.0 inches

Antioxidant 0.01 to 0.0015

Water clarifier 0.01 to 0.02

Latex copolymer 8.0 to 16.0

Surfactants, fungicides and defoamers also may be added to the slurry.

The following examples will serve to illustrate the invention with moreparticularity to those skilled in the art.

EXAMPLE 1 A. Preparation of core or seed copolymer

    ______________________________________                                        Charge       Charge                                                           Instructions Order    Material       Parts                                    ______________________________________                                        Initial charge        Deionized water                                                                              89.25                                    heat to 135° F.                                                                              Hampene Na 3 (40%)                                                                           0.05                                                  1        Dowfax 2A1 (15%)                                                                             0.195                                                          Monawet MB45 (45%)                                                                           2.25                                                           Fumaric Acid   0.75                                                           Potassium Persulfate                                                                         0.30                                     React for 45 min. @                                                                        2        Styrene        7.50                                     135° F. then charge                                                    ______________________________________                                    

B. Preparation of coverpolymer or shell copolymer

    ______________________________________                                        Charge       Charge                                                           Instruction  Order    Material       Parts                                    ______________________________________                                        React 75 min.         Styrene        7.33                                     then charge  3        Sulfole 120    0.06                                                  4        Butadiene      7.58                                     Charge @ 16 ± 1%   Styrene        7.33                                     T.S.C.       5        Sulfole 120    0.06                                     Raise temp to 160° F.                                                                        Butadiene      7.58                                                  6        Glycidyl Methacrylate                                                                        0.38                                                  7        Deionized Water                                                                              2.00                                     Charge @ 22% ± 1                                                                        8        Styrene        7.33                                     T.S.C.                Sulfole 120    0.06                                                           Butadiene      7.58                                                  9        GMA            0.38                                                  10       Deionized Water                                                                              2.00                                     Charge @ 27% ± 1   Styrene        7.33                                     T.S.C.                Sulfole 120    0.06                                                  11       Methacrylic Acid                                                                             0.75                                                           Butadiene      7.58                                     Charge @ 32% ± 1   Styrene        7.33                                     T.S.C.       12       Sulfole 120    0.06                                                           Butadiene      7.58                                                  13       GMA            0.38                                                  14       Deionized Water                                                                              2.00                                     Charge @ 35% ± 1   Styrene        7.33                                     T.S.C.       15       Sulfole 120    0.06                                                           Butadiene      7.58                                                  16       GMA            0.38                                                  17       Deionized Water                                                                              2.00                                     Charge @ 37% ± 1                                                                        18       Deionized Water                                                                              2.74                                                           Potassium Persulfate                                                                         0.10                                                           Deionized Water                                                                              3.62                                                  19       Drew L-198     0.15                                                           DEHA (85%)     0.20                                     ______________________________________                                        PHYSICAL PROPERTIES                                                                     Blowover    Stripped                                                % TSC       46.19                38.5                                         pH          3.01          353                                                 S.T.        50.6          446                                                 B.V.        69.0           20                                                 % Turb.     58             57                                                 Prefloc     1.9%                                                              Filterability                                                                             good                                                              Totals:  Core               8.21   parts                                               Shell              91.75  parts                                               Bd                 45.48  parts                                               Sty                51.48  parts                                               GMA                1.52   Parts                                               MAA                .75                                                        FA                 .75                                               ______________________________________                                    

EXAMPLE 2 A. Preparation or core or seed copolymer

    ______________________________________                                        Charge       Charge                                                           Instruction  Order    Material       Parts                                    ______________________________________                                        Initial charge        Deionized water                                                                              89.25                                    heat to 135° F.                                                                              Hampene Na 3 (40%)                                                                           0.05                                                  1        Dowfax 2A1 (15%)                                                                             0.195                                                          Monawet MB45 (45%)                                                                           2.25                                                           Fumaric Acid   0.75                                                           Potassium Persulfate                                                                         0.30                                     React for 45 min.@                                                                         2        Styrene        7.50                                     135° F. then charge                                                    ______________________________________                                    

B. Preparation of coverpolymer or shell copolymer

    ______________________________________                                        Charge       Charge                                                           Instruction  Order    Material       Parts                                    ______________________________________                                        React 75 min.         Styrene        7.2                                      then charge  3        Sulfole 120    0.06                                                  4        Butadiene      7.47                                     Charge @ 1 h % ± 1 Styrene        7.2                                      T.S.C.       5        Sulfole 120    0.06                                     Raise temp to 160° F.                                                                        Butadiene      7.47                                                  6        Glycidyl Methacrylate                                                                        0.75                                                  7        Deionized Water                                                                              2.00                                     Charge @ 22% ± 1   Styrene        7.2                                      T.S.C.       8        Sulfole 120    0.06                                                           Butadiene      7.47                                                  9        GMA            0.75                                                  10       Deionized Water                                                                              2.00                                     Charge @ 27% ± 1   Styrene        7.2                                      T.S.C.                Sulfole 120    0.06                                                  11       Methacrylic Acid                                                                             0.75                                                           Butadiene      7.47                                     Charge @ 32% ± 1   Styrene        7.2                                      T.S.C.       12       Sulfole 120    0.06                                                           Butadiene      7.47                                                  13       GMA            0.75                                                  14       Deionized Water                                                                              2.00                                     Charge @ 35% ± 1   Styrene        7.2                                      T.S.C.       15       Sulfole 120    0.06                                                           Butadiene      7.47                                                  16       GMA            0.75                                                  17       Deionized Water                                                                              2.00                                     Charge @ 37% ± 1                                                                        18       Deionized Water                                                                              2.74                                                           Potassium Persulfate                                                                         0.10                                     React to 47-49% T.S.C. then add post                                                            Deionized Water                                                                              3.62                                                    19     Drew L-198     0.15                                                           DEHA (85%)     0.20                                         ______________________________________                                        PHYSICAL PROPERTIES                                                                          Blowover   Stripped                                            % TSC          46.61      53.0                                                pH             3.71       3.45                                                S.T.           47.1       47.2                                                B.V.           59         159                                                 % Turb.        54         51                                                  Prefloc        3.1%                                                           Filterability  good                                                           Totals:  Core               8.25   parts                                               Shell              91.75  parts                                               Bd                 44.82  parts                                               Sty                50.70  parts                                               GMA                3.00   Parts                                               MAA                .75                                                        FA                 .75                                               ______________________________________                                    

EXAMPLE 3 A. Preparation of core or seed copolymer

    ______________________________________                                        Charge       Charge                                                           Instruction  Order    Material       Parts                                    ______________________________________                                        Initial charge        Deionized water                                                                              89.25                                    heat to 135° F.                                                                              Hampene Na3 (40%)                                                                            0.05                                                  1        Dowfax 2A1 (15%)                                                                             0.195                                                          Monawet MB45 (45%)                                                                           2.25                                                           Fumaric Acid   1.50                                                           Potassium Persulfate                                                                         0.30                                     React for 45 min.@                                                                         2        Styrene        7.50                                     135° F. then charge                                                    ______________________________________                                    

B. Preparation of over copolymer or shell copolymers:

    ______________________________________                                        Charge       Charge                                                           Instruction  Order    Material       Parts                                    ______________________________________                                        React 75 min.         Styrene        7.2                                      then charge  3        Sulfole 120    0.06                                                  4        Butadiene      7.47                                     Charge @ 27% ± 1   Styrene        7.2                                      T.S.C.       5        Sulfole 120    0.06                                     Raise temp to 160° F.                                                                        Butadiene      7.47                                                  6        Glycidyl Methacrylate                                                                        0.75                                                  7        Deionized Water                                                                              2.00                                     Charge @ 22% ± 1                                                                        8        Styrene        7.2                                      T.S.C.                Sulfole 120    0.06                                                           Butadiene      7.47                                                  9        GMA            0.75                                                  10       Deionized Water                                                                              2.00                                     Charge @ 27% ± 1   Styrene        7.2                                      T.S.C.       11       Sulfole 120    0.06                                                           Butadiene      7.47                                     Charge @ 32% ± 1   Styrene        7.2                                      T.S.C.       12       Sulfole 120    0.06                                                           Butadiene      7.47                                                  13       GMA            0.75                                                  14       Deionized Water                                                                              2.00                                     Charge @ 35% ± 1   Styrene        7.2                                      T.S.C.       15       Sulfole 120    0.06                                                           Butadiene      7.47                                                  16       GMA            0.75                                                  17       Deionized Water                                                                              2.00                                     Charge @ 37% ± 1                                                                        18       Deionized Water                                                                              2.74                                     T.S.C.                Potassium Persulfate                                                                         0.10                                     React to 47-49% T.S.C. then add post                                                            Deionized Water                                                                               3.62                                                   19     Drew L-198     0.15                                                           DEHA (85%)     0.20                                         ______________________________________                                        PHYSICAL PROPERTIES                                                                          Blowover   Stripped                                            % TSC          47.16      52.0                                                pH             3.19       3.26                                                S.T.           43.8       43.7                                                B.V.           72.5       121                                                 % Turb.        53         55                                                  Prefloc        15.7%                                                          Filterability  good                                                           Totals:  Core               9.00   parts                                               Shell              91.02  parts                                               Bd                 44.82  parts                                               Sty                50.70  parts                                               GMA                3.00   parts                                               FA                 1.50                                              ______________________________________                                    

EXAMPLE 4 A. Preparation of core of seed copolymer

    ______________________________________                                        Charge        Charge                                                          Instruction   Order   Material       Parts                                    ______________________________________                                        Charge to reactor                                                                           1       Deionized water                                                                              73.419                                   Set agitation to      Itaconic Acid  0.50                                     250 RPM, purge well   Hampene Na3 (40%)                                                                            0.05                                                           Potassium Persulfate                                                                         0.25                                                           Dowfax 2A1 (15%)                                                                             0.14                                                           Monawet MB45 (45%)                                                                           0.50                                                           Di Sodium Phosphate                                                                          0.50                                     Heat reactor to 135° F.,                                                             2       Styrene        7.50                                     then pull full vacuum                                                         and charge                                                                    ______________________________________                                    

B. Preparation of over copolymer or shell copolymer

    ______________________________________                                        Charge       Charge                                                           Instruction  Order   Material        Parts                                    ______________________________________                                        React 90 min., take  Styrene         6.667                                    TSC sample and charge                                                                      3       Sulfole 120     0.09                                     Raise temp. to 170° F.                                                                      Butadiene       8.083                                                         Deionized Water 5.328                                    React 65 min.                                                                              4       Dowfax 2A1 (15%)                                                                              0.20                                     Take sample for %    Sodium Hydroxide                                                                              0.05                                     T.S.C., then charge  (50%)                                                                         Styrene         6.667                                                         Sulfole 120     0.09                                                  5       Glycidyl Methacrylate                                                                         1.50                                                          Butadiene       8.083                                                 6       Deionized Water 4.426                                    React 62 min.        Dowfax 2A1 (15%)                                                                              0.10                                     then take sample for Styrene         6.667                                    % T.S.C. and charge                                                                        7       Sulfole 120     0.09                                                          Butadiene       8.083                                                 8       Deionized Water 2.566                                                         Dowfax 2A1 (15%)                                                                              0.10                                     React 65 min. then   Styrene         6.667                                    take sample for %                                                                          9       Sulfole 120     0.09                                     T.S.C. and charge    Methacrylic Acid                                                                              0.50                                                          Butadiene       8.083                                                 10      Deionized Water 4.71                                                          Dowfax 2A1 (15%)                                                                              0.15                                     React 66 min. then   Styrene         6.667                                    take sample for %                                                                          11      Sulfole 120     0.09                                     T.S.C. and charge    Glycidyl Methacrylate                                                                         1.50                                                          Butadiene       8.083                                                 12      Deionized Water 4.993                                                         Dowfax 2A1 (15%)                                                                              0.20                                     React 65 min. then   Sulfole 120     0.09                                     take sample for %                                                                          13      Butadiene       8.083                                    T.S.C. and charge                                                             React 90 min., take                                                                        14      Deionized Water 4.74                                     T.S.C sample and     Potassium Persulfate                                                                          0.10                                     charge               Deionized Water 0.113                                    React 2 hrs, then                                                                          15      Sodium Hydroxide                                                                              0.39                                     charge and mix 15    (50%)                                                    min. Cool to room    Dowfax 2A1 (15%)                                                                              0.35                                     temp. and add DEHA   Drew L-198      0.15                                     filter and run B/O                                                            prop.                                                                                      16      Deionized Water 2.17                                                          DEHA (85%)      0.20                                     Rotovac 1 qt @ 150°-                                                                17      Deionized Water 0.575                                    160° F.       Proxel GXL (25%)                                                                              0.05                                     then cool and add post                                                        filter and run stripped                                                       properties                                                                    Batch charged and followed to complete in 10.7 hours.                         ______________________________________                                        PHYSICAL PROPERTIES                                                                          Blowover   Stripped                                            % TSC          43.14      42.96                                               pH             8.48       8.38                                                S.T.           47.6       47.6                                                B.V.           18.5       20                                                  % Turb.        48         48                                                  Prefloc        .24%                                                           Filterability  very good                                                      Totals:  Core               8.00    parts                                              Shell              92.00   parts                                                                 100.00                                                     Butadiene          48.498  parts                                              Styrene            47.502  parts                                              Itaconic acid      0.50    parts                                              Glycidyl Methacrylate                                                                            3.00    parts                                              Methacrylic acid   .50     parts                                                                 100.00                                            ______________________________________                                    

For Examples 1 to 4 conversions of monomers to polymers were about 98 to100%. After stripping, total solids were about 38 to 53%.

NOTES FOR EXAMPLES 1 to 4

Hampene Na3--Ethylenediaminetetraacetic acid-sodium salt, sequestrant orchelating agent.

Dowfax 2A1--Na-dodecyldipheylacid-disulfonate.

Monawet MB45--Di-isobutylsodiumsulfosuccinate.

Sulfole 120--T-dodecyl mercaptan, Phillips Petroleum Co.

Drew L-198--Defoamer, Drew Chemical Co.

DEHA--Diethylhydroxylamine, Shortstop.

PROXEL GXL--Fungicide/bactericide, ICI Americas(1-2-benzisothiazolin-3-one).

Bd--Butadiene.

Sty--Styrene.

GMA--Glycidyl methacrylate.

MAA--Methacrylic acid.

FA--Fumaric acid.

IA--Itaconic acid.

EXAMPLE 5

Aqueous slurries were prepared from, on a dry parts-by-weight basis:

    ______________________________________                                        Kraft wood pulp    13.0                                                       Compounding ingredients                                                       Pulpex P, Grade A-DC                                                                             1.00                                                       polyethylene particles                                                        NARVON F-3 clay    15.70                                                      Afton clay         36.60                                                      Dicalite (not clay)                                                                              18.00                                                      Glass fibers       1.50                                                       Antioxidant        0.1                                                        Water clarifier, KYMENE                                                                          0.0125                                                     Latexes            14.0                                                       Latex copolymer (various)                                                 

The slurries containing also a fungicide were flocculated with acationic flocculant and then cast onto wire screens to remove the waterto form sheets which were compressed, heated, and cooled to form feltsor mats which were then tested.

The anionic core-shell copolymer binder latices used were the followingcopolymers (parts by weight of monomers);

    ______________________________________                                        I. Control:                                                                   45.5            Butadiene                                                     51.5            Styrene                                                       .5              Itaconic acid                                                 .5              Methacrylic acid                                              3.0             Acrylamide                                                    II. Latex of the Invention:                                                   51.5            Styrene                                                       45.5            Butadiene                                                     .75             Fumaric acid                                                  .75             Methacrylic acid                                              1.50            Glycidyl methacrylate                                         III. Latex of the Invention:                                                  50.3            Styrene                                                       44.45           Butadiene                                                     .75             Fumaric acid                                                  1.50            Methacrylic acid                                              3.00            Glycidyl methacrylate                                         IV. Latex of the Invention:                                                   50.7            Styrene                                                       44.8            Butadiene                                                     1.5             Fumaric acid                                                  3.0             Glycidyl methacrylate                                         V. Latex of the Invention:                                                    51.5            Styrene                                                       45.5            Butadiene                                                     1.5             Fumaric acid                                                  1.5             Glycidyl methacrylate                                         ______________________________________                                    

TESTS ON PAPER FELTS OR MATS

                  TABLE A                                                         ______________________________________                                              Wt               Flocculant   Williams                                                                             Drain                              Latex in     Slurry    Wt in Gms                                                                             CSF  Freeness                                                                             Time                               Binder                                                                              Gms    °C.                                                                           pH   1st  2nd  CC   Sec    Sec                            ______________________________________                                        I     30.91  37.0   6.89 199  27   540  37     1.58                           II    36.36  39.2   7.23 179  33   550  28     1.68                           III   33.67  38.4   7.22 205  42   580  28     1.53                           IV    26.92  38.5   7.17 229  30   630  18     1.45                           V     30.46  39.9   7.00 163  30   520  32     1.75                           ______________________________________                                                                         Hot   Hot                                    Latex Sheet    Thickness Density Tensile                                                                             Tensile                                Binder                                                                              Wt       Inches    Lbs/Ft.sup.3                                                                          Lbs   Elong %                                ______________________________________                                        I     22.94    0279      48.67   13.36 2.37                                   II    24.82    0299      49.29   16.47 2.97                                   III   24.91    0289      50.97   17.81 3.44                                   IV    25.07    0271      50.17   16.73 3.12                                   V     22.34    0281      48.51   13.38 2.60                                   ______________________________________                                              Cold     Cold                   Heat                                    Latex Tensile  Tensile   Split Strength Lb                                                                          Aging                                   Binder                                                                              Lbs      Elong %   Max    Mean    Sec                                   ______________________________________                                        I     21.06    2.42      35     45      109                                   II    25.46    3.87      41     50      102                                   III   30.96    4.49      50     65       76                                   IV    23.72    3.60      41     53      300                                   V     26.20    3.86      49     41       74                                   ______________________________________                                    

Other tests on felts using polymeric latices made with glycidylmethacrylate on a co-monomer in the shell of the core-shell copolymershowed heat aging time of 276, 310, 492 and 504 seconds, respectively.These results show unusually high heat aging for latices containingglycidyl methacrylate as compared to a control latex. Also the laticescontaining glycidyl methacrylate gave felts with higher cold tensilestrengths than the control.

What is claimed is:
 1. A paper felt or mat comprising about, on adry-weight basis, a predominant amount of finely divided clay or talcparticles, minor amounts of polyethylene particles, glass fibers,antioxidants and biocides, from 5 to 20 parts of kraft wood pulp andfrom 8 to 16 parts of a core-shell copolymer of:A. A core of copolymermade from about 6 to 8 parts of at least one vinyl aryl monomer havingfrom 8 to 10 carbon atoms and from about 0.5 to about 8 parts of atleast one dicarboxylic acid monomer selected from the group consistingof fumaric acid, itaconic acid, or a combination of fumaric acid anditaconic acid; and B. A shell of a copolymer made from about 40 to 60parts of at least one vinyl aryl monomer having from 8 to 10 carbonatoms, from 60 to 40 parts of at least one conjugated diene monomerhaving from 4 to 6 carbon atoms, from 1.5 to 5.0 parts of at least oneglycidyl monomer selected from the group consisting of glycidylacrylate, glycidyl methacrylate, or a combination of the glycidylacrylate and glycidyl methacrylate, and from 0 to 2.0 parts of at leastone monocarboxylic acid monomer selected from the group consisting ofacrylic acid, methacrylic acid, or a combination of acrylic acid andmethacrylic acid, wherein the core copolymer comprises from about 7.5 to10.5 parts and where the shell copolymer comprises from about 92.5 to89.5 parts of the core-shell copolymer, all parts of monomers in thecore-shell copolymer adding up to about 100 parts.
 2. A paper felt ormat according to claim 1 wherein the core-shell copolymer, the vinylaryl monomer is selected from the group consisting of styrene,alphamethyl styrene, paramethyl styrene, methyl vinyl toluene, p-vinyltoluene and 3-ethyl styrene and the conjugated diene monomer is selectedfrom the group consisting of 1,3-butadiene, isoprene, piperylene,2,3-dimethyl-1,30butadiene. pentadiene and hexadine.
 3. A paper felt ormat according to claim 2 wherein the core-shell copolymer, the vinylaryl monomer is styrene, the conjugated diene monomer is 1,3-butadienethe dicarboxylic acid monomer is fumaric acid, the monocarboxylic acidmonomer is methacrylic acid and the glycidyl monomer is glycidylmethacrylate.